Defect annihilation in AlN thin films by ultrahigh temperature processing

Postgrowth thermal processing in the range of 1200-1400 degrees C is shown to improve markedly the quality of thin (similar to 200 nm) AlN films grown by molecular beam epitaxy on SiC substrates. Comparison of both on-axis (0002) and off-axis (10(1) over bar 2) x-ray diffraction peaks documents this improvement. Cross-sectional transmission electron micrographs confirm the reduction in dislocations and grain boundaries, while plan-view micrographs demonstrate that threading defect densities can be reduced to similar to 3 x 10(8)/cm(2) after annealing. The thermal treatment is particularly effective because of the unusually large temperature window between the onset of a near-zero reactant sticking coefficient at similar to 1200 degrees C and AlN thermal decomposition at similar to 1400 degrees C. The Al sticking coefficient and the AlN decomposition rate are also reported. (C) 2000 American Institute of Physics. [S0003-6951(00)01114-1].